$(window).load(function(){

    // We are listening for the window load event instead of the regular document ready.

    function animSteam(){

        // Create a new span with the steam1, or steam2 class:

        $('<span>',{
            className:'steam'+Math.floor(Math.random()*2 + 1),
            css:{
                // Apply a random offset from 10px to the left to 10px to the right
                marginLeft	: -10 + Math.floor(Math.random()*20)
            }
        }).appendTo('#rocket').animate({
            left:'-=28',
            bottom:'-=100'
        }, 120,function(){

            // When the animation completes, remove the span and
            // set the function to be run again in 10 milliseconds

            $(this).remove();
            setTimeout(animSteam,10);
        });
    }

    function moveRocket(){
        $('#rocket').animate({'left':'+=20'},1000).delay(1000)
            .animate({'left':'-=20'},1000,function(){
                setTimeout(moveRocket,1000);
            });
    }

    // Run the functions when the document and all images have been loaded.

    moveRocket();
    animSteam();
});